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SBUS decoder limitations
- Thread starter bbardon
- Start date
Probably easier to run 4 PWM servo cables, another issue with Sbus is you will be powering 4 servos from one servo cable. Most Sbus advice recomends running a sepearte Bec to power the Sbus servos seperatly and not use the power provided from the receiver.
Yep, Sbus is handy, but you always want to watch power loads with or without sbus. We see people adding more and more servos into their planes as they get larger and more complex models in the hobby, but still feeding it all via a single BEC plugged into a receiver. Please keep in mind that those plugs are limited to about 10 amps for a short period of time. The cheapest solution is to add some parallel wires to distribute the power to different parts avoiding any bottlenecks.
I may be the guinea pig here and try it anyway. It is for a 2 meter 6 digital servo thermal sailplane, not a 3D aerobat. Servos will be EMAX ES3352. 90+% of the time maybe three servos at most will be demanding significant power. Power will be coming from an (advertised) 4A BEC ESC. I'll bench test for sure. I'll take the advice of this group, but given the added info, do you think I would be asking for trouble to try it?
Trying this on the ground presents no issues.
The Emax servos do not draw much power, so not so worried about the Sbus power here, but a little concerned with just 4 amps from the BEC. Is it feeding 8 servos in all, or just the 6 in the wing?
Very simple test, run all of the servos back and forth a bunch and see if you get any issues. We have seen some BECs not even reach advertised rating. The units we sell at Aloft have all been great, most able to meet double the rated power for short periods. The exception tends to be the VERY small Dualsky unit, it doesn't seem happy to provide beyond its rating. (In general issues with the very small units from China is the norm.) I know we lost one plane to a failed small BEC even though it tested fine on the ground. Probably built up some heat in flight...
Always a good idea to plug in an amp meter to see what loads are being put onto the BEC.
Also, you mention that this is a 6 servo wing, so safe to say you have some flaps in there. A common issue we see people get into with flaps is running the servo up against a mechanical limit of the flap. When you do this, the servo will DRAW it max power it can trying to push through the mechanical limit. This will result in several bad results. First one being too much load on the power source, and possible brownout for the entire model. Second is over heating the servo and killing it. And if you are running a strong serco, the chances of a mechanical failure are very high. That can be popping the servo free, breaking linkage, or breaking the flap. We have seen and or heard of all of these issues on a rather steady rate. It is always best to avoid hitting any mechanical limits! Sneak up on them during setup, and when you see no more possible movement, back off a bit for safety margin.
Hope this helps some folks..
Very simple test, run all of the servos back and forth a bunch and see if you get any issues. We have seen some BECs not even reach advertised rating. The units we sell at Aloft have all been great, most able to meet double the rated power for short periods. The exception tends to be the VERY small Dualsky unit, it doesn't seem happy to provide beyond its rating. (In general issues with the very small units from China is the norm.) I know we lost one plane to a failed small BEC even though it tested fine on the ground. Probably built up some heat in flight...
Always a good idea to plug in an amp meter to see what loads are being put onto the BEC.
Also, you mention that this is a 6 servo wing, so safe to say you have some flaps in there. A common issue we see people get into with flaps is running the servo up against a mechanical limit of the flap. When you do this, the servo will DRAW it max power it can trying to push through the mechanical limit. This will result in several bad results. First one being too much load on the power source, and possible brownout for the entire model. Second is over heating the servo and killing it. And if you are running a strong serco, the chances of a mechanical failure are very high. That can be popping the servo free, breaking linkage, or breaking the flap. We have seen and or heard of all of these issues on a rather steady rate. It is always best to avoid hitting any mechanical limits! Sneak up on them during setup, and when you see no more possible movement, back off a bit for safety margin.
Hope this helps some folks..
Thanks, Wayne. All good info.
It's a four-servo wing, six servos in all. I use Mike Shellim's Esoar template on my trusty X9D (I think that Tx was my first purchase from Aloft, way back in the day) so all travels are carefully set.
I've scoured the web for the Sbus decoder and the channel programmer. At the end of it all, Henny was right. It will be easier to run 4 cables. The decoder is hard to source, the channel programmer more so (there's an Arduino sketch that some people have had success with, others not so much.) Is Sbus a dying/dead protocol? Has anything else taken its place? I'm sticking with my ACCST stuff for now, so I'll keep it simple and press on.
When do you expect your next shipment of Emax ES3352s to come in?
As always, great support from Aloft!
All the best.
It's a four-servo wing, six servos in all. I use Mike Shellim's Esoar template on my trusty X9D (I think that Tx was my first purchase from Aloft, way back in the day) so all travels are carefully set.
I've scoured the web for the Sbus decoder and the channel programmer. At the end of it all, Henny was right. It will be easier to run 4 cables. The decoder is hard to source, the channel programmer more so (there's an Arduino sketch that some people have had success with, others not so much.) Is Sbus a dying/dead protocol? Has anything else taken its place? I'm sticking with my ACCST stuff for now, so I'll keep it simple and press on.
When do you expect your next shipment of Emax ES3352s to come in?
As always, great support from Aloft!
All the best.
We stock the Sbus decoders.
alofthobbies.com
We should have these back in stock Monday or Tuesday with our main FrSky shipment.
The programmer is no longer produced as I recall the newer Ethos radios can do this for you. I have not tried this to confirm. If you like we could preprogram one for you to watch for whatever channels you would like. Pretty sure we still have an old school programmer too.
Emax - Think they are on the way.
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The programmer is no longer produced as I recall the newer Ethos radios can do this for you. I have not tried this to confirm. If you like we could preprogram one for you to watch for whatever channels you would like. Pretty sure we still have an old school programmer too.
Emax - Think they are on the way.
MikeB
Very Strong User
Im using the SBUS decoders on a twin where I have four servos on the left side and three running on the other decoder on the right. Hitec 5245mg on all with each decoder having its own sbus channel port on the receiver. I checked with Aloft on this and they said no problem. I do have custom leads made with larger gauge servo wires for a multiconnector that feed each decoder.
Excellent!
So to sum it up, many options now:
Ethos after 1.7 is released
A FrSky STK unit
ErskyTx on a number of transmitters
Arduino Nano or Arduino Pro Mini
Awesome!!
Thank you Mike! You are a machine!!
